I had this problem with my '04 WJ with Automatic Zone Climate Control. There is lots of heat available, but only on the passenger side. Driver's side was getting only cold air. Pretty uncomfortable at -20C!

The blend doors for the heater and A/C could be broken, and JGCparts.com has info on checking for that and replacing broken blend doors if necessary. But before you do all that....try this.

Calibrate the AZC door actuators as follows:
- Turn ingnition on
- Set AZC to automatic
- Turn ignition off
- Remove the IOD fuse from the Power Distribution Center (the manual shows you where this fuse is located) Wait several seconds, then reinstall the IOD fuse.
- Turn ingition on. Do not touch any of the AZC controls for at least one minute to allow the calibration function to run to completion.

There are additional details on JGCparts.com for AZC self-diagnostics too, to check for blend door function, and at the very end of the site, a drawing to help locate the IOD fuse.

Give it a try. Costs nothing, takes five minutes, and if your problem is only the actuator function you can have full AZC back fast......and nice toasty warm air on those cold winter nights!